Nwokoro Charles Chigemezu, Kreye Christine, Necpalova Magdalena, Adeyemi Olojede, Busari Mutiu, Tariku Meklit, Tokula Mark, Olowokere Florence, Pypers Pieter, Hauser Stefan, Six Johan
Department of Environmental Systems Science, Group of Sustainable Agroecosystems, Swiss Federal Institute of Technology, ETH Zurich, CH-8092, Zurich, Switzerland.
National Root Crops Research Institute, Umudike, Nigeria.
Field Crops Res. 2021 Oct 1;272:108283. doi: 10.1016/j.fcr.2021.108283.
Cassava-maize intercropping is a common practice among smallholder farmers in Southern Nigeria. It provides food security and early access to income from the maize component. However, yields of both crops are commonly low in farmers' fields. Multi-locational trials were conducted in Southern Nigeria in 2016 and 2017 to investigate options to increase productivity and profitability through increased cassava and maize plant densities and fertilizer application. Trials with 4 and 6 treatments in 2016 and 2017, respectively were established on 126 farmers' fields over two seasons with a set of different designs, including combinations of two levels of crop density and three levels of fertilizer rates. The maize crop was tested at low density (LM) with 20,000 plants ha versus high density (HM) with 40,000 plants ha. For cassava, low density (LC) had had 10,000 plants ha versus the high density (HC) with 12,500 plants ha.; The fertilizer application followed a regime favouring either the maize crop (FM: 90 kg N, 20 kg P and 37 kg K ha) or the cassava crop (FC: 75 kg N, 20 kg P and 90 kg K ha), next to control without fertilizer application (F0). Higher maize density (HM) increased marketable maize cob yield by 14 % (3700 cobs ha) in the first cycle and by 8% (2100 cobs ha) in the second cycle, relative to the LM treatment. Across both cropping cycles, fertilizer application increased cob yield by 15 % (5000 cobs ha) and 19 % (6700 cobs ha) in the FC and FM regime, respectively. Cassava storage root yield increased by 16 % (4 Mg ha) due to increased cassava plant density, and by 14 % (4 Mg ha) due to fertilizer application (i.e., with both fertilizer regimes) but only in the first cropping cycle. In the second cycle, increased maize plant density (HM) reduced cassava storage root yield by 7% (1.5 Mg ha) relative to the LM treatment. However, the negative effect of high maize density on storage root yield was counteracted by fertilizer application. Fresh storage root yield increased by 8% (2 Mg ha) in both fertilizer regimes compared to the control without fertilizer application. Responses to fertilizer by cassava and maize varied between fields. Positive responses tended to decline with increasing yields in the control treatment. The average value-to-cost ratio (VCR) of fertilizer use for the FM regime was 3.6 and higher than for the FC regime (VCR = 1.6), resulting from higher maize yields when FM than when FC was applied. Revenue generated by maize constituted 84-91% of the total revenue of the cropping system. The highest profits were achieved with the FM regime when both cassava and maize were grown at high density. However, fertilizer application was not always advisable as 34 % of farmers did not realize a profit. For higher yields and profitability, fertilizer recommendations should be targeted to responsive fields based on soil fertility knowledge.
木薯与玉米间作是尼日利亚南部小农户的常见做法。它保障了粮食安全，并能使农户较早从玉米作物中获得收入。然而，在农户的田地里，这两种作物的产量通常都很低。2016年和2017年在尼日利亚南部进行了多点试验，以研究通过增加木薯和玉米的种植密度以及施肥来提高产量和盈利能力的方法。2016年和2017年分别进行了4次和6次试验，在两个季节里，于126块农户田地上采用了一系列不同的设计，包括两种作物密度水平和三种施肥量水平的组合。玉米作物在低密度（LM）条件下种植，每公顷20000株，在高密度（HM）条件下种植，每公顷40000株。木薯方面，低密度（LC）为每公顷10000株，高密度（HC）为每公顷12500株；施肥方式采用有利于玉米作物的方案（FM：每公顷施90千克氮、20千克磷和37千克钾）或有利于木薯作物的方案（FC：每公顷施75千克氮、20千克磷和90千克钾），还有不施肥的对照（F0）。与LM处理相比，较高的玉米密度（HM）使第一季可销售玉米棒产量提高了14%（每公顷3700个玉米棒），第二季提高了8%（每公顷2100个玉米棒）。在两个种植周期中，施肥使FC和FM方案下的玉米棒产量分别提高了15%（每公顷5000个玉米棒）和19%（每公顷6700个玉米棒）。由于木薯种植密度增加，木薯块根产量提高了16%（每公顷4吨），施肥（即两种施肥方案）使其产量提高了14%（每公顷4吨），但仅在第一个种植周期如此。在第二季，相对于LM处理，玉米种植密度增加（HM）使木薯块根产量降低了7%（每公顷1.5吨）。然而，施肥抵消了高玉米密度对块根产量的负面影响。与不施肥的对照相比，两种施肥方案下的新鲜块根产量均提高了8%（每公顷2吨）。木薯和玉米对肥料的反应因田地而异。在对照处理中，随着产量增加，积极反应趋于下降。FM方案的肥料使用平均价值成本比（VCR）为3.6，高于FC方案（VCR = 1.6），这是因为施用FM时玉米产量高于施用FC时。玉米产生的收入占种植系统总收入的84 - 91%。当木薯和玉米都高密度种植且采用FM方案时，利润最高。然而，施肥并不总是明智的，因为34%的农户没有实现盈利。为了获得更高的产量和盈利能力，应根据土壤肥力知识，针对有反应的田地提出施肥建议。
